Update source code to match its gem

[viliampucik]

The latest blankslate gem [https://rubygems.org/gems/blankslate/versions/3.1.2] is newer than the current repo code. Please would it be possible to update the repo code?

Please note that the gem is missing test/preload.rb file from its parent - builder gem.

The gem also contains leftover test files from its parent: test/test_eventbuilder.rb, test/test_markupbuilder.rb, test/test_method_caching.rb, test/test_namecollision.rb and test/test_xchar.rb.

[viliampucik]

Closed in favor of #11.